The applicants proposed to evaluate a new algorithm for ultrasound B-scan image formation. The algorithm is based on a hybrid continuous-discrete state imaging model that represents the effects of abrupt changes in attenuation and scatterer density as the transducer pulse propagates across tissue boundaries and through cystic and calcified structures. The applicants reported having tested the approach on phantom data and obtained substantial improvements in B-scan resolution and contrast. They expect the algorithm to result in improved imagery in a broad range of applications. The applicants proposed to focus evaluation on transrectal prostate imaging with the goal of demonstrating significantly improved prostate zonal differentiation. The resulting imagery could enable physicians to better estimate prostate volume and identify the zones in which lesions are located or hypertrophy is occurring, capabilities important in the diagnosis of prostate-related medical problems. The applicants proposed to evaluate the algorithm using synthetic, phantom, and canine prostate pulse echo characteristics and their relationship to histology. They would collect the pulse-echo data using three GE transducers, including a recently introduced Microslice probe, and will experimentally determine the improvement in the ability of clinicians to differentiate prostate anatomical structures. Following a successful evaluation in Phase I, they would develop the algorithm for real-time operation in Phase II.